Buyer Guide

Generators Buyer Guide

Generators are essential pieces of equipment providing portable or stationary electrical power for jobsites, remote operations, and backup needs. They are critical for contractors, rental companies, emergency services, and any business requiring reliable off-grid or supplemental power.

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Fast facts

Used price range for commercial-grade units: $5,000 - $75,000+
Operating weight ranges from 500 lbs (small mobile) to 20,000 lbs+ (large stationary/towable)
Typical hours-of-life: 10,000 - 30,000 hours for well-maintained diesel units.
Fuel usage varies significantly by load and size, from 0.5 GPH for small units to 10+ GPH for large industrial generators.
Common accessories include fuel tanks, distribution panels, transfer switches, and sound attenuation enclosures.
Jobsite uses: power tools, temporary lighting, office trailers, pumps, welding equipment, and emergency backup power.
Available in diesel, natural gas, propane, and gasoline configurations, with diesel being most common for heavy-duty applications.
Power output ranges from 10 kW to 2,000 kW+, dictating application suitability.

What to look for

1Check the engine for excessive smoke, oil leaks, and unusual noises; a healthy engine is paramount.
2Inspect the alternator/generator head for physical damage, corrosion, and signs of overheating; ensure windings are clean.
3Examine the control panel and instrumentation for functionality, missing gauges, and water intrusion.
4Verify proper voltage and frequency output under load; use a resistive load bank if possible.
5Assess the fuel system for leaks, sediment in filters, and the condition of the fuel tank.
6Review service records meticulously for consistent oil changes, filter replacements, and any major repairs.
7Investigate the cooling system: check radiator fins for damage, coolant levels, and signs of leaks.
8For trailer-mounted units, inspect tires, brakes, lights, and the hitch assembly for roadworthiness.
9Hour meter red flags: excessively low hours for an older unit (potential tampering) or extremely high hours without major rebuilds.
10Telematics data can reveal operational patterns, load factors, and fault codes, providing insight into past usage.

Best makes & models

Caterpillar

CAT XQ series, C-series

Known for robust diesel engines, exceptional durability, and global parts/service availability, making them a preferred choice for heavy-duty applications.

Cummins

Power Generation (QSF, QSK series)

Offers highly reliable and fuel-efficient engines with strong performance and a wide range of power outputs suitable for diverse industrial needs.

Generac

Industrial Series, Protector Series

A popular choice for both standby and prime power, offering a comprehensive line of generators with strong innovation in control systems and natural gas options.

Kohler

Decision-Maker, KD Series

Provides dependable and quiet operation with advanced digital controls, often favored for rental fleets and applications requiring stable power.

Atlas Copco

QAS series, QEP series

Recognized for their portable, robust, and fuel-efficient generators designed for demanding jobsite conditions with easy serviceability.

Models with known issues

Commonly-reported issues from operators and technicians. Every machine varies — always inspect before you buy.

Certain lesser-known brands Various import models pre-2010

Industry chatter occasionally notes challenges with parts availability and technical support for older, less established import brands, leading to downtime issues.

Specific compact gasoline units Small recreational/contractor models

Reports sometimes highlight issues with carburetor clogging and fuel system degradation on smaller gasoline units not properly stabilized or stored, especially after prolonged disuse.

Certain older diesel models Some pre-Tier 4 interim engines

Occasionally, units from this era can have more complex or troublesome emissions control systems, leading to higher maintenance costs if not diligently serviced.

Frequently asked questions

What is a reasonable price for a used commercial generator?

Prices can range from $5,000 for smaller 20-30kW units to $75,000+ for large 500kW+ industrial models, heavily dependent on age, hours, and condition.

How many hours on a generator is too many?

For well-maintained commercial diesel generators, 10,000-15,000 hours is mid-life, while 20,000+ hours is considered high but still viable if the unit has been properly serviced or rebuilt.

Can I finance a used generator?

Yes, many equipment lenders offer financing for used generators, often requiring a down payment and approving based on credit history and the equipment's value.

What's the typical cost to ship a generator?

Shipping costs vary widely based on size, weight, and distance, but can range from a few hundred dollars for local transport of smaller units to several thousands for cross-country or specialized hauling of large industrial generators.

Do used generators come with a warranty?

Typically, private sales of used generators are 'as-is,' but some dealers may offer limited warranties on certified pre-owned units for an additional cost or for a short duration.

How does buying a used generator affect its resale value?

Buying used means a lower initial depreciation hit; maintaining good service records and keeping the unit in good condition will help preserve its future resale value significantly.